Development of continuous flow analysis based on nonionic surfactants-iron(III) thiocyanato complex for the determination of nonionic Surfactants in river water

Solvent-extraction spectrometory is widely used to determine polyoxyethylene non-ionic surfactants (NS). The method is based on the formation of a complex between a NS and cobalt(III) or iron(III) thiocyanate. We reported on a continuous-flow analysis (CIA) with iron (III) thiocyanate to simplify the procedure and to reduce the amount of reagents in manual solvent-extraction spectrometory. Toluene and a water sample containing NS were flowed to an extraction coil (i.d. 1 mm x 3.12 m) at 2.02, 2.90 mL min(-1), respectively, to extract NS into toluene. Then, toluene containing NS and a potassium thiocyanate (6 M)-iron(III) chloride (24 mM) mixed solution were flowed to the reaction coil (i.d. 1 mm x 1.04 m) at 2.02, 0.42 mL min(-1), respectively. Those flows were segmented with air bubbles. The absorbance of NS-iron(III) thiocyanate complex formed in the toluene layer was measured at 505 nm. The detection limit of this CFA was 2 mu mol L-1 as heptaoxyethylene dodecyl ether. Good results were obtained in recovery tests using river water.